This invention relates to a heat exchanger configuration for an air conditioning pack of an aircraft air conditioning system.
Aircraft air conditioning system packs have ram air cooled heat exchangers that provide the heat sinks for the air flow which is being cooled prior to being supplied to the aircraft cabin. A typical pack has a primary heat exchanger that rejects heat generated by compressing the ambient air to the required pack inlet pressure. The pack also includes a secondary heat exchanger that rejects heat generated by the air cycle machine (ACM) compressor.
Each of the heat exchangers are sized for worst case conditions, which do not apply throughout most of the operation of the air conditioning pack. For example, the primary heat exchanger is sized for a high altitude/cruise condition, and the secondary heat exchanger is sized for a hot day/ground operation. Sizing the heat exchanger for these worst case conditions results in much larger heat exchangers than is necessary for most pack operating conditions. As a result the overall heat exchanger configuration is inefficient in that it takes up more space and provides more weight than is necessary.
Therefore, what is needed is an improved heat exchanger configuration for an aircraft air conditioning system pack.